A. Field of the Invention
This invention relates to the field of solenoid operated electrohydraulic poppet valve assemblies and methods for making them.
B. Background Art
Prior solenoid operated valve assemblies as disclosed, for example, in U.S. Pat. No. 3,737,141 are formed of an upper valve housing having a low magnetically permeable spacer brazed or welded between a ferromagnetic end stop section and a ferromagnetic body section. This welding or brazing has been objectionable in that the weldments or brazements formed slag in the inner armature bore of the valve housing. In addition, weld flux or brazing compound has been deposited in the bore. Accordingly, machining has been required to remove the slag and weld flux or brazing compound formed within the inner armature bore. Additionally, machining has been required to straighten the bore due to off-center distortion caused by welding or brazing. Thereafter, expensive refinishing of the armature bore has been essential. All of these operations have required the use and availability of highly skilled machinists and operators and have been very costly and time consuming. Since the armature bore is effectively hidden, quality control has been difficult and costly.
A further problem has been that objectionable pin holes have been formed in the weldment which may not show up until the valve assembly reaches the actual user in the field. At that time such pin holes have caused problems or actual failure. For example, flux has been formed in the pin holes and then after being blown out by the high pressure these pin holes create leaks in the valve.
A still further disadvantage of prior valve assemblies has been that they could not be disassembled or repaired in the field. In order to make repairs in the field, for example, the entire welded or brazed valve housing would have to be replaced and this replacement was in effect a replacement of the entire valve assembly.
Accordingly, an object of the present invention is a solenoid operated poppet valve assembly having a valve housing which is formed of individually machined and finished threaded sections. The sections may be threadedly assembled and tested to form desired valve assemblies by an OEM manufacturer such as a farm machinery company without requiring the use of machine tools or highly skilled machinists and operators.